1. Field of the Invention
This present invention relates generally to techniques for performing wellsite operations. More specifically, the present invention relates to techniques for monitoring the operation of blowout preventers (BOPs), for example, involving determining a ram block location.
2. Description of Related Art
Oilfield operations are typically performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Once the downhole tools form a wellbore to reach a desired reservoir, casings may be cemented into place within the wellbore, and the wellbore completed to initiate production of fluids from the reservoir. Tubing or pipes are typically positioned in the wellbore to enable the passage of subsurface fluids to the surface.
Leakage of subsurface fluids may pose a significant environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), are often positioned about the wellbore to form a seal about pipes therein to prevent leakage of fluid as it is brought to the surface. In some cases, the BOPs employ rams and/or ram blocks that seal the wellbore. Some examples of ram BOPs and/or ram blocks are provided in U.S. Pat. Nos. 4,647,002, 6,173,770, 5,025,708, 7,051,989, 5,575,452, 6,374,925, 2008/0265188, 5,735,502, 5,897,094, 7,234,530 and 2009/0056132. The location of the ram and/or ram block of a BOP may be measured by visually looking at a tail shaft of the ram blocks. Ram position sensors may be provided as described, for example, in U.S. Pat. Nos. 2008/0197306, 4,922,423, 5,320,325, 5,407,172, and 7,274,989.
Despite the development of techniques involving BOPs and/or ram blocks, there remains a need to provide advanced techniques for monitoring BOP operation. The present invention is directed to fulfilling these needs in the art.